linux-kernel - Re: [PATCH v7 4/4] tty: serial: 8250: add DFL bus driver for Altera 16550.

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Date:   Tue, 20 Dec 2022 19:09:20 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     matthew.gerlach@...ux.intel.com
Cc:     hao.wu@...el.com, yilun.xu@...el.com, russell.h.weight@...el.com,
        basheer.ahmed.muddebihal@...el.com, trix@...hat.com,
        mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        tianfei.zhang@...el.com, corbet@....net,
        gregkh@...uxfoundation.org, linux-serial@...r.kernel.org,
        jirislaby@...nel.org, geert+renesas@...der.be,
        niklas.soderlund+renesas@...natech.se, macro@...am.me.uk,
        johan@...nel.org, lukas@...ner.de, ilpo.jarvinen@...ux.intel.com,
        marpagan@...hat.com, bagasdotme@...il.com
Subject: Re: [PATCH v7 4/4] tty: serial: 8250: add DFL bus driver for Altera
 16550.

On Tue, Dec 20, 2022 at 08:36:52AM -0800, matthew.gerlach@...ux.intel.com wrote:
> From: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
> 
> Add a Device Feature List (DFL) bus driver for the Altera
> 16550 implementation of UART.

In general the code here looks good to me, but one thing to discuss due to
comment to the previous patch(es).

...

> +	u64 *p;
> +
> +	p = dfh_find_param(dfl_dev, DFHv1_PARAM_ID_CLK_FRQ);
> +	if (!p)
> +		return dev_err_probe(dev, -EINVAL, "missing CLK_FRQ param\n");
> +
> +	p++;
> +	uart->port.uartclk = *p;

So, here and the below is using always the second u64 from the returned data.
Does it mean:
- we always skip the first u64 from the returned buffer and hence... (see below)
- we may actually return the second u64 as a plain number (not a pointer) from
  (an additional?) API? In such case we would not need to take care about this
  p++; lines here and there.
- we have fixed length of the data, returned by find_param(), i.e. 2 u64 words?

-- 
With Best Regards,
Andy Shevchenko